Apparatus for making expanded sheet material



Jan. 23, 1968 R. D. PITSCH APPARATUS FOR MAKlNG EXFANDED SHEET MATERIAL Filed March l5, 1966 Ww; Wgjm/ BY Mami WMM ATTORNEYS United States Patent O 3,364,519 APPARATUS FOR MAKING EXPANDED SHEET MATERIAL Ronald D. Pitsch, Oshkosh, Wis., assignor to American Excelsior Corporation, a corporation of Delaware Filed Mar. 15, 1966, Ser. No. 534,498 3 Claims. (Cl. 182) ABSTRACT OF THE DISCLOSURE Apparatus for foaming a heat foamable sheet material in which the sheet material is directed in a path during which it is continuously contacted with .heated friction means so as to promote the foaming and corresponding thickening while retarding lateral shrinkage of the sheet due to its friction contact with the heated friction means.

This invention relates to an apparatus for foaming a heat foamable sheet material of preselected lateral width which permits expansion in thickness due to the foaming but substantially restricting resulting shrinkage of the material in this lateral width.

It is common practice to foam a heat foamable sheet material such as a synthetic plastic of which polystyrene is an excellent example by incorporating foaming agents of well known types into the material and then heating to cause the foaming which produces a cellular sheet material. These foaming agents are customarily activated by heat so that the usual practice has been to heat the sheet in a hot fluid such as steam or hot Water.

A disadvantage of this method of foaming is that the expansion of the foaming agent to form cells in the sheet material causes an increase in thickness of the sheet material which of course is desired but simultaneously causes a lateral shrinkage of the material. This defect is successfully overcome by the present invention.

One of the features of this invention is to provide an apparatus for foaming a heat foamable sheet material of preselected lateral width While retarding lateral shrinkage of the sheet material which would normally result by the increase in thickness due to foaming.

Another feature of the invention is to provide such an apparatus wherein a principal heat applying means is a heated friction means which also retards lateral shrinkage of the sheet because of the friction contact with the heated friction means.

Other features and advantages of the invention will be apparent from the following description thereof taken in conjunction with the accompanying drawing. This drawing is a vertical, sectional, semi-diagrammatic View partially in elevation for clarity of illustration and showing one apparatus for practicing the invention.

In the illustrated apparatus a polystyrene sheet which may be for example 30 mils thick and contains a foaming agent such as dissolved pentane is guided to a chamber 11 which is preferably insulated against excessive heat losses as by top and bottom 12 and side 13 heat insulating material.

In the chamber 11 the sheet is directed over heated friction means here shown as a series of adjacent heated rotatable rolls 14, 15 and 16. These rolls are internally steam heated and comprise heated friction means as the rolls are in contact with the sheet 10 over a sufficient area, here shown as considerably greater than 180, so that a friction contact is set up even when the rolls are made of polished steel or similar metal.

As is shown in the single figure each roll except the first roll and the last roll 16 is in adjacent relationship with two other rolls so that the sheet 1t] passes directly from one roll to the next without an intervening passing of any considerable extent through space where the sheet would be unsupported by a roll. This results in the sheet 10 expanding as it picks up heat from the internal heated rolls but being restricted in its tendency toward lateral shrinkage as a result thereof because the sheet is substantially never out of contact with a roll until substantially full expansion has been accomplished.

In order to permit the expansion in thickness of the sheet even with the close relationship of one roll to the next and in order to accommodate different thicknesses of sheet material, alternate rolls in the illustrated embodiment are provided with yielding mounting means which permit movement of these alternate rolls away from and toward the next roll or rolls. As is illustrated in connection with the alternate rolls 15 and shown in detail in the last roll in this series this yielding mounting means can comprise oppositely located springs 17 bearing against a movable end block 18 that rotatably supports each end of an axle 19 on which each roll is mounted. The last roll 16 in the series is similarly mounted on similar springs 20 and 21 but because of its relationship with its next adjacent roll 14 the mounting is positioned for vertical movement of this last roll 16.

The entire series of rolls 14, 15 and 16 are positively driven in any customary and well known manner so as to draw the sheet 10 over the rolls and through the chamber 11.

During the travel of the sheet material 10 over the series of heated friction rolls 14, 15 and 16 means are provided for projecting a heated atmosphere against the surface of the sheet material that is opposite the surface in contact with the roll. Thus as is shown in the illustrated embodiment there are provided elongated tubular spray nozzles 22 adjacent the path of travel of the material 10 over the rolls and adapted to spray steam, indicated at 23, in contact with the surface of the sheet that is opposite the surface contacted by a roll. The sheet is of course also heated by steam within the insulated steam chamber 11 which is replenished by the steam emitted from the nozzles 22.

As the now expanded sheet material leaves the last roll 16 in the series it is conveyed from the chamber 10 by cooperating carrier chains 24 to a location (not shown) where the sheet can be embossed or otherwise shaped by shaping 0r molding means. The heated sheet leaves the chamber 10 by Way of an insulated exit 25.

The invention disclosed and claimed herein is related to that disclosed and claimed in the copending application of D. I. Gasch et al. Ser. No. 424,899, iiled Jan. l2, 1965 and assigned to the same assignee as the present application. This earlier application discloses and claims the basic apparatus and method for foaming heat foamable sheet material.

Having described my invention as related to the embodiment shown in the accompanying drawing, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. Apparatus for foaming a heat foamable sheet material of preselected substantial lateral width, comprising: means for directing said sheet material in a path in which foaming takes place; means for continuously contacting a lateral surface of said sheet material with a heated friction means While in said path, said heated friction means comprising a series of adjacent heated rotatable rolls having friction surfaces over which said sheet passes in immediate succession, said friction means thereby causing heat foaming of said sheet material while retarding 3 lateral shrinkage thereof by reason of said friction contact; means forming an enclosing heated atmosphere chamber surrounding said series of heated rolls; and means in said chamber for projecting heated atmosphere against the surface of said sheet material that is opposite the one in con tact with a roll,

2. Apparatus for foaming a heat foamable sheet material of preselected substantial lateral width, comprising: means for directing said sheet material in a path in which foaming takes place; means for continuously contacting a lateral surface of said sheet material with a heated friction means while in said path, said heated friction means comprising a series of adjacent heated rotatable rolls having friction surfaces over which said sheet passes in immediate succession, said friction means rolls thereby causing heat foaming of said sheet material while retarding lateral shrinkage thereof by reason of Said friction contact, each roll other than the first and last in said series being in said adjacent relationship with two other rolls; and yielding mounting means for alternate rolls in said series for permitting accommodation of sheet material of varying thicknesses in the areas between adjacent rolls.

3. The apparatus of claim 2 wherein there are provided means forming an enclosing heated atmosphere chamber surrounding said series of heated rolls, and means in said chamber for projecting heated atmosphere against the surface of said sheet material that is opposite the one in contact with a roll.

References Cited UNITED STATES PATENTS 1,590,638 6/1926 Marquette 18--2 XR 1,850,061 3/1932 Jones 18-2 XR 2,350,772 6/1944 Klute et al. 18-2 2,651,242 9/1953 Neely 18--2 XR 2,771,388 11/1956 Rocky et al, 18--2 XR WLLIAM I. STEPHENSON, Primary Examiner. 

